Process of making cement



June 17, 1941. H. B. JOHNSON 2,246,253

PROCESS OF MAKING CEMENT Filed NOV. 18, 1957 5 SheeVlZS-Sheet 1 CEMENT /O M/NFPALI UO% X4 June 17, 1941. H. B. JOHNSON 2,246,253

PRooEss oF MAKING CEMENT Filed Nov. 18, 1957 5 sheets-sheet 2 June 17 1941- H. B. JOHNSON PROCESS OF MAKING CEMENT Filed NOV. 18, 1937 5 Sheets-Sheet 3 Filed Nov. 18, 1937 5 Sheets-Sheet 4 IIIIL DMN www@

`une 17, 1941.

H. B. JOHNSON 2,246,253

PRocEss oF MAKING CEMENT Filed Nov. 18, 1937 5 sheets-sheet 5 5 7' 019.4625 J 7019465 J 7' OPAE JTOPHE Patented June 17, 1941 2,246,253 Pnocnss or MAKING' CEMENT A Herbert B. Johnson, Rochester, N.' YY., assigner to Ritter Products Corporation, Rochester, N. Y.,V a

corporation of New York Application November 18, 1937,.Serial No. 175,299

s cams.` (o1. 10e-,1am

My inventiony relates, generally,'to the manufacture of cement and it particularly relates to the recombining, compounding, and proportion'- atelymixing of the mineral constituents used in raw mixes for the manufacturefof Portland and other cement products and applies to the prod? ucts which have been produced through the concentration or separation of associated minerals such as described in my copending application, Serial No. 151,950, led July 3, 1937, now Patent No. 2,197,864, of which this application is a continuation in part.

In my copending application, I have disclosed how the cement minerals may be separated electrostatically into different discrete portions. One of these portions compri-ses an Alzoa'group, another is a CaCO; group and another is an SiO-i group, which are termed respectively alumina, limestone and silica groups or products. These products are combined in varying quantities either alone or with a raw cement mineral product in order to meer different cement specifica-- tions depending upon 'the particlilarf recmire-k ments Vof these specifica-tions and the chemical analysis of the separated portions and of the 'raw cement minerals combined therewith.

` 'My invention applies Aparticularly to the ce-r' ment rock deposits :of Pe-nnsylvaniajNew Jersey,V and New York where, in many cases", vthere is al deciency in the limestone minerals andan eX"- cess of silica, alumina, magnesia, and other minerals. ACement manufacturers, particularly in the Lehigh and lChester valley districts in Pennsylvania, and also in NewA York and New Jersey, are uitallyconcerned with the deficiency of limestone-andexcessalumina and magne'sia minerals in their deposits. Inmany cases, this necessitates the purchase of limestone from outside vsources which `'increases their production cost from `c to"1f5 per barrel of cement produced. Many cement yoperations in the districts referred to have been abandoned Von account'of the high production :costs resulting from a deficiency Ain limestone minerals and the high cost of purchasing .and delivering these necessary minerals to their plants.

'For a long time this `'situation 'has interested cement .manufacturers Aarid ='engineers in the possibility lof -corrcentratingtl'xisjraw cement rock and other vraw :materials and byproduct.s,'with the object of decreasing or eliminating, throng-h such concentration, .the excess' silica, jal-umina, and `Jzcagnesia, and therebyYincreasing'the limestone content .iso that purchase fof *limestone from outside sources `would be sunneccsary'. The concentrating cost is much less than the cost of purchasing and ldelivering these materials so that,A by the'use of proper concentrating methods, thev cement manufacturer becomes independent :oi outside sources of supply, reduces his production costs, increases his flexibility of control, and imi-,v`

proves his salable cement products.

The art of concentration properly applied' to cement operations results in the opening upof' many deposits and makes possible the future operation of many plants which are now idle." `At the same time the concentration of raw minerals used inmanufacturing cement represents several new problems for the cement chemistandthose responsible for operations, particularly in'. the

recombination ofthe separated mineral elements'.

in accordance with standard and special x-Well known formulae. Cement manufacturers-fwho' are purchasing addi-tional limestone have to' deal with the impurities not only in their own quarries' but also with the impurities vin the; additional limestone purchased 'from' f outside sources, Therefore, in some cases, it is necessary to deviate` somewhat from standard raw mi-X formulae nto meet a vcertain vset of conditions. At 4the same;

time the buyersfof the finished cement product arel setting'upspecications or'requirements lthat are becoming more and more difficult to'meet' dueI ment rock and other raw cement materials present new problems to thecement manufacs. turer which are principally of mechanical rather than of chemical'nature. y 7 f An object of myinvention is to provide for meeting any cement specication, either stand# ard or special, without requiring a special'set'up 'or' adjustment of the apparatus employed-in separating the cement minerals into certain distinct portions. I

Another object of my inventionV is tofprovide for separating raw cement minerals as' they'a-re obtainedfromv a cement quarry into -predeter mined discrete' portions'according to the con` stituents of the quarry minerals and rfor recom-4A bini-ng these discrete portionsV to meet any standard or special cement specifications Without 'requir-ng any change in the equipment employed for separating the raw'cementv minerals. Still ano'ther'object of my invention is to'disassociate the steps 'employed in separating raw cement minerals from the steps employedin rre# combining them to make' different cement specifi# cations so that it is only necessary to change the recombining steps and not the separating steps in changing from one cement specification to another.

My invention is also particularly directed to the special treatment of the alumina products that are produced in the concentration of raw cement minerals. High silica cements are usually slow in` setting and of good tensile strength.

High alumina cements are usually quick setting and quick hardening. alumina are hard to burn properly, due to the fusibility of the calcium aluminate at suchV4 high temperatures which causes agglomeration and sticking of the clinker. Iron oxides, suchv as hematite, tend to lower theV burning tempera- Cements too high in proper temperature, and" before they come into close contact where the acids and basic elements assist to produce a more uniform cement clinker.

ture and, within certain limits, assist in the production of sound cement although excessiron 1.

aiects the color of the cement.

The essential elements of Portland cement are silica and lime. Alumina increases the uidity of the mix during clinkering, thereby simplifying the .burning operations and somewhatreducing" the temperature required. Also, alumina adds somewhat to the plasticity of'cementpbut, ifv used' in excess, Vit directly speeds up 'the setting time: Alumina and iron minerals have little value inY cement exceptl as iiuxing agents, thereby accelerating the actual combination of the lime and silica at proper temperatures during clinkerinto-discrete portions 'and to recombine them in the raw `material mix in such manner that their fluxing action during the subsequent clinkering operation vis materially improved and the resulting cement product is notV deleteriously affected.

My ,invention is also particularly directed to. the mechanical preparation and recombination ofv cement raw mix minerals which have been previouslyf separated andritalso provides for the:

special treatment 'of the alumina product, or fluxlng minerals, so that much better control of the fusing' action of the limestone and silicais' accomplished with the minimum use of these iluxing minerals, thereby producing a much more uniform clinker and reducing, to some extent, the'amount of gypsum used for correcting the setting time of the finished cement.V f

I have found that the alumina product, which is easily separated out` electrostatically,l asV described in my application referred to hereinbefore, has a much lower `degree of grindability than has the limestone or silica. I have compared the grindability of an original raw cement mix, prepared from cement rock, ,andthe iirst concentrates or alumina product produced by electrosta-tic concentration. i These' materials were Yboth screened through 100 -mesh` and were passed through a colloidmill having a clearance of .0002 andrat a'dilution of one-half part Water toone part solids. Powerconsumption was considerably higher'for grinding the original material and the average :particle size was only reduced to approximately Vten microns."1"he rst concentrataor alumina product produced 'in concentration, required much less power and wasground under the same` conditions Aas the original raw cement mix-'but it was easily lo# I takethe rst concentrate produced in separation-and after sampling, weighing, and putting in storage, pass this material as required through ,a colloid'mill of suitable type. From the colloid 'mill' discharge, I pass the product through pressure Yspray nozzles so that it is sprayed, like paint, to cover the particles of lime and silica when in suspension. This is done preferably whentheyaregdischarged from an" elevator or screw'conveyor into `therecombination storage mixing bin,l or just prior, to entering theV kilns after the iinalj grinding; It is-desirablej .to spray this-,material on the .coarser sized particles vwhile in air suspension, such as Vwhile they are dropping froIn-the ,-elevatorlor-conveyor, in order` to paint orcoat each-particle thoroughly and, by spraying, thereby preventing the colloidal fluxing minerals from balllingf up or forming cakes While coming in contact with thedry mixture. lA-Ldispersing agent may be employed which prevents the colloidal particles from coagulating and interfering with best spraying, spreading, or coating action. This dispersing agent should be mixedwith-the wateradded to the feed for the colloid mill which regulates the properdilution and obtains maximum grinding and dispersion of the mineral particles. -The addition of the colloidal fiuxing agent increases the moisture or watercontent of the raw mix; vFor example, the fluxing agent at `a dilution of .5:1 to 1:1 causes an increase of the average moisture con'- tent of the raw mix approximately 8 per cent.

f This prevents the colloidal substance from escaping or getting` off of the particles during final grinding operations prior to entering the kiln for clinkering. Upon entering the kiln,ithis'col loidal substance will yadhere to thelime and silica mineralsy until the `raw1nix,at proper temperature, begins to ball Aup prior toentering the clinkering zone in the kiln. Therefore, on account ,of the even distribution'of the iiowing minerals throughout the raw mixjthereV is little loss of the uxing .materiaL Vthrough circulation of air through the kiln, during kilnoperation and, at proper temperature for clinkering. The particles Vof lime and silica are evenly coated with the fiuxing agent so that proper `combination thereof is made at minimum :temperature and with a minimumof fuelbeing required. Obviously the nished-clinker willbe much more uniform than-it would be if the. uxing-'materials were added in the dry'state. `This is due principally to theY fact that, in vspraying the iinely ground colloidal iluxing minerals intoy the falling stream of raw mix: minerals which are much coarser in size, a better mixing and covering power is availablethan .Would beY possible by mixing these materials of the same size in a dry state..` f

A further object ofmy invention is to provide for grinding the iluxing minerals tov a colloidal state and to thoroughly coat the particles of lime and ysilica with the iiuxing agent Vthus formed before the raw mix is delivered to the kiln for clinkering.

Other objects of my invention will, in part, beobvious and in part appear hereinafter.

For a more complete understanding of the nature and scope of my invention, reference may be had to the following detailed description taken in connection with the accompanying drawings,

in which:

Figure 1 illustrates, diagrammatically, how different separations may be obtained in the use of the electrostatic separator; and

Figures 2 through 6 illustrate flow sheets that may be employed in practicing my invention.

Referring now particularly-to Figure 1 of the drawings, it will be observed that I have there shown, diagrammatically, an electrostatic separator. This separator is of the type that is illustrated and described in'detail in myrcopending application Serial No. 128,097, filed February 27, 1937, now Patent No. 2,135,716, and assigned to the assignee of this application, It comprises a plurality of pairs of rotating electrodes X and Y. Preferably these electrodes are generally cylindrical in shape and arerelatively long, forr example, from six to eight feet long. The electrodes may be-maintained at a high difference of uni-directional voltage by a suitable source of direct current such asa mechanical rectier or an electric Valve rectifier. As disclosed inV my copending application, Serial No. 151,950, now Patent No. 2,197,864 of which this application is a continuation in part, the electrodes X and Y may be divided into different groups for each of which different polarities and voltages may be `employed as may bestv suit the particular separating conditions.

As shown in the 'drawingsfthe raw cement imnerals are 'fed into a hopper I0 in the proper state for most ecient electrostatic separation. The raw cementminerals are first fed into close proximity with electrodes Y of theirst group II which are maintained at a positive potential,

as indicated, relative tothe electrodes This' first group of electrodes II may comprise'three pairs of electrodes that are maintained at a difference of potential of about 6,000 volts.

At this voltage a rst concentrate comprising the fluxing minerals, principally A1203, is thrown out and carried away by'a material conveyor I2'. This conveyor may be of the screw type, as illustrated. While the first concentrate is composed principally offAlOa, there will also be some of the other cement minerals presen-t but in considerably less proportions than in the original raw cement minerals. Iron minerals, in the form of pyrites, will also be present in theY flux'ing minerals that 'are thrown out'as a result of the iirst separation by the rst group I I of electrodes X and Y. i

The balance of the rcement minerals are then subjected to the electrostatic'elds maintained between the next group I3 of electrodes X and Y in which the X electrodes are maintained at a positive potential relative to' the Y electrodes and preferably at a potential difference ofabout 12,000 volts. In this group the cement raw materials are fed into close proximity with the negative Y electrodes.Y At the bottom of this' group of electrodes, a second anda third concentrate may be removed by the product 'conveyors I4 and I5 respectively. The second concentrate will contain a large percentage cf SiOz silicates while the third concentrate will' contain a high percentage of CaCOa or lime. I

. operating conditions.

The remaining portion of the raw cement minerals is then fed between the pairs of electrodes X and Y of the third group I6 in which the-Y' electrodes are maintained at a positive potential with respect to the X electrodes and at a poten-A tial difference of about 18,000 volts. In this group the rawV cement minerals are fed into close proximity with the positive `Y electrodes with the result that the cement minerals are separated into middlings and tailings that are carried away by product conveyors I1 and I8 respectively. The middlings contain principally CaCOa and SiO2 silicates and are returned to be reprocessed through Vthe separator. The tailings comprise principally hard quartz which may be reprocessed cr discarded as waste material.

While the rst groupI I of electrodes comprises three' pairs, the second group I3 comprises six pairs, and the third group I6 comprises four pairs, it will be obvious that different numbers may be employed in each group without departing -from the scope of my invention. Also the polarities of the electrodes in the various groups may be changed as will best suit a given set of Also, different voltages may be employed as may be desired. The particular arrangement of electrodes, and polarities and voltages used are set forth for illustrative purposes and are representative of what I have '1 found to be the best for a particular set of conditions and analysis ofraw cement minerals.

In the iiow sheet shown in Figure 2, I have shown an arrangement of equipment for preparing the cement raw minerals for electrostatic separation, for removing the impalpable dust after grinding, and for storing the separated products'A made by the electrostatic separation andthe dust for subsequent recombination, as desired. As shown, each product is automatically and continuously sampled and it is also automatically and continuouslyweighed by recordingv scales of either the dump type or conveyor type before it entersits storage bin. In this manner at any time the recorded weights may be taken for a shift, a day, or any period oi operation,

and computed with the chemical analysis' of the various minerals fora particular period of operation. This will place the operator at all times in a position to know the exact 'tonnage and i mineral content of each bin.

The materials as drawn from the storage bins pass through adjustable automatic feedersand again through automatic weighing machines. These feeders may be adjusted from experience so that the proper weights are assured 'in proical analysis `of the quarry rock that is being processed. Suitable adjustments may be made in the separating equipment to obtain the de-r sired separated products. With agiven separat-v ing setup, quarry-stool; of vvarying chemical analysis may be processed and the separated-products Chemists and operators in stored indifferent bins, the :contents 4and chemicallanalysis of eachA offwhichfwill be readilyavailable ,to the: operator "or: cement.- chemist;l When itis desired-:tomeet a given: cement specification, it istonl-y necessary to Withdraw from 4the different bins-the'necessary quantitiesin accordance-with their chemical analysis; Therefore, theseparatingrsteps v-may -b`e carried' out entirely independently of the recombining steps.v given. cement specification itA is unnecessaryto alterthefoperationof the entire'flowrsheet but ratherritisgmerelyfnecessary towithdraw from the-'different storagev bins, the desired amounts of :raw-cement minerals having." known chemical analysis andzto recombine them preparatory to performing the clinkering operation. Likewise the, separatingV steps maybe carried out without particular**consideration*being givenY to any particularacement specification that it maybe necessarytomeet; It is-then-unnecessary to: select particularpartsvof the quarry rock for processingffandsin .mostcases the general run of mine roclcmayfloeemployed.y As aresult the cost of quarrying isfmateriallyreducedand at the sametirnewthe lifev ofthequarry is materially pro longedfby makingv available portions of it which were' previouslyconsideredY -unt for economical use inmanuf-acturing cement.

Referring again to the flow sheet` shown inV EigurefZ, itwil-lbe observed that, after being sampled,.weighed,: and properly-'proportioned, the fluxinggminerals in. the'irst concentrate product, composed principally of A1203, are mixed with a4 suilcient'quantity of dispersingV agent, such as sodium carbonate, and Waterto form a solution-ffofvfrom-t'l torlzl which is sufficient to cause-the1 solids to flow through thev colloid` mill satisfactorily; I prefer to use a colloid mill of tl1'e=-.Premier- Mill type, which works on the principle.` of .particle-bombardment rather than otherztypesfwhich Work on theprinciple of abra--i sionfalthough these other types may be employed without Vdeparting, fromv the .scope of the 'present invention.

The colloidal: sludgeobtained from the colloidv mill vhasf a' great covering power as indicated herein-before; It-ispumped under pressureV land appliedfthroughspray dischargenozzles to the rawl cement minerals prior to vclink'ering. As shown these raw mix minerals are obtained from acombination of theN second and Ythird concentrates-with the'dust product obtainedfrom the secondarygrinding operation prior to electrostatic separation. The combination of these products is-in accordancewith the analysis of the-nalicementproduct' that itis desired to obtainnAfter-the dry products are mixed ina suitablemechanical mixer, theV colloid sludge is applied? thereto eitherv before going through'the pulverizer, or after they leave the'pulverizer or just-.before-the mixisconveyed to the kiln vfor the-iclinker-ing operation. v

As illustrated inthe flow sheet shown in 1Figure 3, the rst concentrate containing the fluxing minerals may be 'further concentrated.l Whether or not this Aadditional concentrating step of these mineralsis desirable depends rupon the analysis offzthe particular rock that is-being processed and the-degree ofseparation that can he obtained in.- the first instance; This additional concentration -step of the iluxing minerals-may be employed prior to their being placedY in solution and ground in the co-lloid mill. The fluxing agent in colloid :form is then. sprayed into the recombined raw/'mixA minerals asv described.

For a.

The flow sheet. illustrated .iiIfFigureA 4i shows: that the original dust, after being properlyfsamepled.: and weighed; may: be processed' with. the fluxing minerals. so: that the two Aproducts may beground .together and reduced togcoll'oidal'size. Through pressure spraying-apparatus. the rcombinedjdust and'uxing minerals in: the colloidal statemay loel combined with the` coarser` parti- `cles before or after pulverizing or justrbefore the rawn cement mix'visv conveyed'to? the kiln for clinkering. Inv this 'i manner a larger percentage of the raw mix inthe'wet'stateri's .evenlyisprayed andmixed with the. coarserparticles ofthe separated products containingprincipally the CaCQs tion mf a Vrotating type: kiln Ywillv be' reduced.y to a' minimumibecause ofthe evenly distributed addition ofzmoistur'e to thef: d'ry'mixture.V Since this moisturev is thoroughly distributed; it willi then cause:y a'vballi'n'g" up actioni'soon after the recombined cement mineralsentertheil kiln due to theirotatirrg action' thereof.: This will'ireduce theY losses .through air. circulation in the` kiln; The rrely dispersed'. particles will quickly'nbecome baked uponthef coarser particles fandcar.- ried tothe clinkering zone `,Where maximumlfliixing-will takeplace promptly: This thoroughrlis.-y

tribution' andffevenw spreading' ofpztle vfluxingelemlents throughout' thel raw: *mixture produces a much more uniformy clinker'thatis'much'easier to pulverizeY than the clinkers formed;.in vaccordanceA with the :prior :art

cement product will bepbtainable;

The ow Asheet shown -in ,Figurei 5': indicates inamore`detailed`mannerhow the separated raw cementV mineral products 'may 'be recorrrbi ned inthe pro'per proportions to meet adesired'cement specification.. As shown the products resulting from thel electrostatic" separation are stored indifferent bins-to be. drawn off as vdesired; Thel products lfrom'. these storage bins Aare sampled, weighed, and proportioned' by automatic feeders 'before delivery tol elevator A, which itself'does. considerable mixing in deliveringn the combinationY material tofthe top of the raw-'mixture -storage bin B. Asvshownthis materialfmay be. continuously drawn fromif the bottomy ofV thev mixing loin bya mixingV conveyor C'andfreturned to the'top, ofthe bin by elevator D.

Preferably elevators 1A and D discharge the materials at the top of the bin B against'eacli other inA order to 'more thoroughly mix theparticles.: This arrangement for mixing the cement materials' is'particularly convenient in the event that-the cement specicationis changedV or in the event: that yit is desirablefto co-rrectfurther anycombination; of minerals by the'addition of CaCOs, SiOz, or A1203 minerals. Sf'uch additions' of "these minerals asdesired may be drawn from the individual: product bins inthe necessary proportions andfedY into 'conveyor C without interfering with thecontinuous 'operation' of the recombining f apparatus. mixingfbirr `is .then discharged 'therefrom through elevatorlE. i

Obviously.. 'a-fnumber. of"v the raw mixture stor- Therefore, the cost' of theJ clinker .grinding .operationf will 'be Areduced* and at the same time; at more "uniform .resulting TheA mixture vfromv the age bins 'may be employed' meach Yof the flew sheets shown in Figures 2, 3, and 4 for recombining and thoroughly mixing the separated cement minerals and the original-dust. The'numn of raw `mixes ahead` of the kiln'sin order vto4 assure of continuous operation of the plant.

In the flow sheet shown in Figure 6, the preferred method of applying the colloidal uxing minerals is shown. I have found that, on such dry materials as cement minerals, it is preferred to add the finely divided colloidal paste gradually and evenly in order .to obtain optimum coverage of the dry particles. Therefore, the colloidal paste' may be proportionately divided under pressure by using spray nozzles of different capacities. For example; of the total amount added, one-third may be mixed at X, one-third at Y, and one-third at Z. This repeated application of the fluxing mineral sludge permits a more evenV distribution with minimum possibility of balling up action which would otherwise take place when mixing dry Aand wet materials. However, this method is not limited-to any specific number of spray nozzles. Any desired number of different capacities may be used lat the mostl convenient places in the liow sheet a-s will assure the maximum and most uniform coverage of the CaCOa and SiO2 minerals. These nozzles may be full cone, hollow cone, or `flat spray types as may fit operating conditi-ons most suitably.

Since certain further changes may be made in carrying out my invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Iclaim:

l. In the dry method of manufacturing cement, the steps which comprise: successively passing finely divided raw cement mate-rial between a plurality of pairs of .oppositely charged electrodes .and in close proximity to the positive electrodes an-d thereby separating out a fluxing concentrate, successively passing lthe balance of the raw cement material between a plurality of pairs of oppositely charged electrodes and in close proximity to vthe negative electrodes and thereby separating out a CaCO; concentrate, and successively passing the remaining balance of the raw cement material between a plurality of pairs of oppositely charged electrodes and in close proximity to the positive electrodes and thereby separating the same into a hard quartz co-ncentrate and a middling portion containing principally CaCOa and SiO2.

2. In the dry method of manufacturing cement, the steps which comprise: successively passing nely divided raw cement material between a plurality of pairs of oppcsitely charged electrodes and in close proximity to the positive electrodes and thereby separating out a uxing concentrate, successively passing the balance of the raw cement material between a plurality of pairs of oppositely charged electrodes an-d in close proximity to the negative electrodes and thereby separating out a CaOOs concentrate and an SiOz concentrate, and successively passing the remaining balance of the raw cement material between |a plurality of pairs of oppositely charged electrodes and in close proximity to the positive electrodes and thereby separating the Vsame into a hard quartz concentrate and a middling portion `containing principally CaCO; and SiOz. v

3. In the method of manufacturing cement, the steps which comprise: successively passing finely divided raw cement material between a plurality of pairs of oppositely charged electrodes and in .close proximity to those of one polari-ty `to separate out auxing concentrate the A1203 content of whichis substantially higher than that of the original raw cement material, collecting said A1203 concentrate, successively passing the balance of the finely divided raw cement material between a plurality of pairs of oppov-sitely charged f electrodes and in close proximity to those of one polarity to separate thesame into Si02 vand CaCOa concentrates, and Vindividually collecting .the'last named concentrates.

4. In the method .of manufacturing cement, the steps' which comprise: successvevrlyV passing finelyhdivided raw cement material between a plurality of pairs vof oppositely charged electrodes and in close proximity to those of positive polarity to separate out a fluxing concentratethe A1203 content of which is substantially higher than that of theV original raw cement material,

`collecting said A1203 concentrate, successively passing the balance of the finely divided raw cement material between a plurality of pairs of oppositely charged electrodes and in close proximity to those of negative polarity to separate the same into SiO2 and CaCO3 concentrates, and individually collecting the last named concentrates.

5. In the dry method of manufacturing cement the steps which comprise: feeding nely divided raw cement material between a pair of electrodes maintained at a high difference of unidirectional voltage and in close proximity to one of them and thereby separating out a fluxing concentrate, feeding the balance of the raw ce ment material between a pair of electro-des maintained at a high difference of uni-directional voltage and in close proximity to the electrode thereof having a polarity opposite to fthe polarity of the electrode in close proximity to which the material is first fed and thereby separating out a CaCOs concentrate, and feeding the remaining balance of the raw cement material between a pair of electrodes maintained at a high difference of uni-directional voltage and in close proximity to the electrode thereof having the same polarity as the electrode adjacent to which the material is first fed and thereby separating the remaining balance into a hard quartz concentrate and a middling portion containing principally CaCOa and SiOz.

6. In the dry method of manufacturing cef ment the steps which comprise: feeding finely divided raw cement material between a pair of electrodes maintained at a high difference of unidirectional voltage and in close proximity to one of them and thereby separating out a fiuxing concentrate, feeding the balance of the raw cement material between a pair of electrodes maintained `at a high difference of unidirectional voltage and in close proximity to the electrode thereof having a polarity opposite to the polarity of fthe electrode in close proximity to which the material is first fed and thereby separating out a CaCOs concentrate and an S102 concentrate, and feeding the remaining balance of the raw cement material between a pair of electrodes maintained at a high difference of uni-directional voltage and in close proximity to the electrode thereof having thesamepolarity as the electrode-adja- `cent to'which the material is first fed and therefeeding finely divided raw cement material be- `tvveenfa plurality of pairs of electrodes maintained at vahigh difference of uni-directional voltageean-d-.in close proximity `to the electrodes of one polarity and therebyvseparating out a iiuxing concentrate,- successively feeding theb-alance ofthe raw cement material betweenfa plurality ofV pairs l of electrodes y maintained -at a lhigh difference of uni-directional lvoltage and-in close proximity to the electrodes having a polarity opposite to the Y.polarity vof the electrodes i-n Aclose proximity to which the material :is first fed and thereb-yvseparatingout a CaCOsA concentrate, ande successively feeding fthe remaining balance of the rawrcelment material between a plurality of pairs of; electrodesmaintainedfat a high difference off uni-directional voltage and -in.-c1oseproXimity-to the'electrodeshaving the same polarity as the,

electrodes adjacent to-Whichthe material is rst fed .and thereby `separating the 'remaining balance into a hardquartzconcentrate andV a lmididling portion containingprincipallyCaCOa `and SiOz.

8. In the dry -methodpf rmanufacturing fcement, the steps which, comprise: successively feeding finely divided raw cement material vbetween a Aplurality of pairs f of Y= electrodes maintained at a highdiierence :of uni-directional voltage and in close proximity.towthe` electrodes of ione, polali-tyand thereby .separating out 'a luxing concentrate, successively feeding the Vloa-lance oftherraw cement v-xznaterialfbetween a plurality 1 of i pairs of-:electrodes: maintained lat la high f differenceof unidirectional voltage.- and in close .proximity to the A:electrodes n-having fa polarity opposite -to -t-he `-polar-ity of :thefelectrodes inclose proximity to whiche-the .material is` first fed and thereby separating-fouta'CaGIOgconcentrate aand. an -SiO2-.concentrate; and successively feeding.-tl-ierremainingl balance of the ,raw cement -rmaterial ibe'tweenA a, 4plurali-ty V:of pairs --ofelecftrodesmaintained. at a vthigh difference of A1midirectionalvol-tage -fand'` in-l. close `proximity to the electrodes havingy the fsa-mewpolarityflasltheelec- `trodes adja-centtoW-hich Lhe-materiaLisrSt fed -and .thereby g separating l: the l remaining balance intola hard v-quartz1 concentrate .and "a --middling portionF containing principal-.1y` CaCOa -and SiOz.

HERBERT yB JOHNSON 

